At a restaurant a while ago I had a lovely carpaccio of beef which had little chips of black garlic scattered on it. I can't remember what else it was dressed with, but the black garlic worked really well.

You'd have to use heat of some description to kill any botulism spores. Never just drop raw garlic into a bottle of oil to flavour it. It's probably worth googling the best way to flavour oil with garlic.

I wonder which cuisine its comes from, why preserve it in this way, I had a jar given to me years ago which ended up in the bin, I could never get a feel for what I was supposed to it with it either, now I'm thinking Korean or something south east Asian. Might google it tonight or not

Mine came in a jar of brine (?) always thought it was normal garlic which had been pickled or something.
Google said:

"Pye says Bredbo’s black garlic is ‘fermented’ in the oven for 60 days. He uses the term ‘ferments’ loosely because, technically, nothing is added to the white garlic to turn it dark. Instead, there’s a chemical process called the Mallaird reaction at play."

Wikipedia:
Black garlic is a type of aged garlic whose browning is attributable to Maillard reaction rather than caramelization, first used as a food ingredient in Asian cuisine. It is made by heating whole bulbs of garlic (Allium sativum) over the course of several weeks, a process that results in black cloves. The taste is sweet and syrupy with hints of balsamic vinegar[1] or tamarind.[2] Black garlic's popularity has spread to the United States as it has become a sought-after ingredient used in high-end cuisine.[citation needed]
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